Interference fit process development for the ITER Vacuum Vessel Gravity Support mock-up fabrication

The ITER Vacuum Vessel (VV) is supported by the nine VV gravity supports (VVGS) located on the cryostat toroidal pedestal. The VVGS is dual hinge type that fastened by dowel in the hinge-block hole. This paper presents the technical approach and result on the interference fitting process of the sleeve to the full-scaled VVGS mock-up. Since the sleeve and the hinge-block hole have under millimeter tolerance and around two-meter long length, the shrink fit method has been selected for the interference fitting of the sleeve into the hinge-block hole. The duration time for required shrinkage was expected by the simple analytical approach of natural convective heat transfer. The coolant charging method was suggested to secure a sufficient time for the process. The liquid nitrogen was charged to the handling fixture capped sleeve hole's cavity. As a result, the necessary contraction time was secured as thousands of seconds. Consequently, the interference fitting was successfully done for VVGS mock-up fabrication, and the technical solutions will be applied to the VVGS manufacturing.